Know-how

Early in the boating season you’re most likely to encounter advection fog, which develops when the water temperature is lower than the dew point. Later in the season you’re likely to encounter fog that develops when cool air flows over warm water, sometimes called sea smoke. My point is that sooner or later you will run into fog.

In the August 2003 Know-How, I wrote about finding your way in fog using electronics to aid in piloting — GPS, chart plotter, radar. Here, I will cover some of the other issues of boating in fog, from right-of-way to sounding signals.

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1. In conditions of reduced visibility the Rules of the Road pertaining to right of way are suspended. Right of way rules apply only to vessels in sight of one another. There is no right of way until visual sighting occurs.

2. When operating in or near conditions of reduced or restricted visibility all vessels must proceed at a safe speed. That means slowing down even if your boat is equipped with radar. Nowhere does any authority define safe speed, though obviously it is different for a ship displacing 40,000 tons than for a 16-foot runabout. A good rule of thumb is that you should be able to stop in half the distance you are able to see.

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3. Know the fog signals and sound the one appropriate for your situation. When under way (not docked, anchored or aground) and making way (moving through the water), a boat or ship under power must sound one prolonged blast at intervals of not more than two minutes between blasts. (A sailboat motorsailing is under power and considered power driven.) However, don’t sound them at much less than two minutes so you can listen for signals from other vessels or for echoes.

4. If you are under way and stopped (not making way), sound two prolonged blasts about two seconds apart at intervals not exceeding two minutes.

5. All other vessels under way that are, or could be, at some disadvantage when maneuvering sound one prolonged followed by two short blasts (Morse code for D: dash, dot, dot) at intervals of no more than two minutes. Such vessels include those not under command, those towing or pushing another vessel, vessels restricted in their ability to maneuver (dredges and other workboats, for example), commercial fishing boats, and sailboats under sail alone. If manned, a vessel being towed or the last vessel in a line being towed sounds one prolonged followed by three short blasts (Morse B) within two minute intervals, preferably right after the tow vessel has sounded its signal.

6. Pilot boats on duty can sound four short blasts in addition to the signals for a powerboat under way (whether making way or stopped).

7. A boat anchored anywhere but in a designated “special anchorage area” (so noted on a chart) must rapidly ring its bell for four or five seconds every minute. If you hear the rapid ringing of a bell immediately followed by a gong, it’s a ship of more than 300 feet. Vessels at anchor also may sound in succession short, prolonged, short blasts (Morse R) in addition to its bell to warn an approaching vessel of her position and the possibility of collision.

8. A vessel aground must signal three distinct strokes of its bell before and after the signal for a vessel at anchor. Think of those three dings as, “I am aground.” A vessel aground also can sound short, short, long blasts (Morse U) if the possibility of a collision is developing. Morse U is the international signal for, “You are standing into danger.”

9. Sound travels at about 1,100 feet per second. Listening for an echo from your fog signal could indicate an obstacle nearby. Half the number of seconds from your signal to the echo multiplied by 1,000 is the approximate distance.

10. Signal generation is a handy feature on many newer VHF radios. And don’t forget to use your VHF; communication in fog is a good thing.

11. Keep in mind that these points apply to all conditions when visibility is restricted, including heavy rain. Keep a visual and aural lookout posted at all times in such conditions.

12. Remember, there’s more at risk than being lost when operating in fog. The lives of you and your crew, as well as others, could be at risk.